202 Proceedings of the Pk,oyal Physical Society. 
the localities assigned being Ashantee and Guinea. The 
next specimen, Causus Rhomheatus, will also be found in Dr 
Gray's list, p. 163, No. 86, with its synonyms (Hah. West 
Africa ; Gold Coast, Liberia, South Africa) ; but it is, more 
fully described in the catalogue of reptiles of the British 
Museum, 1844 (Snakes, p. 33). Of this snake the British 
Museum possesses four. The specimen named Boodon Geo- 
metricus will be found, with its synonyms, in Dr Gray's list, 
p. 159, No, 42, under the name Bocedon Geometricus, Hah. 
West Africa ; and the specimen named Onychocephalus 
Liherianus will be found with the single synonym Onycho- 
cephalus Liheriensis, under the name Onychopsis Liheriensis, 
in Dr Gray's list, p. 157, No. 18 ; Hah. Liberia, Calabar. 
The last remaining specimen to be noticed is a lizard, 
Tiliqua Fernanda, described in the British Museum Cata- 
logue (p. 110, Lizards) as Tiliqua Fernandi — the Fernando 
Po Tiliqua — of which an interesting account has already 
been given to this Society in a paper by Mr Andrew Murray, 
at p. 415 of the first volume of its Proceedings. The oblique 
cross brown bands along the brown sides should be bright 
scarlet or vermilion, but stuffed or preserved specimens seem 
to lose this brilliant colour, as it is not to be seen in the pre- 
sent specimen, although otherwise in excellent preservation. 
V. On the Silicijication of Organic Bodies. By Alexander Bryson, Esq., 
F.RS.E. 
The solution and deposition of silica has become a very im- 
portant question, not only to the mineralogist, but to the 
physical geologist. Whilst the mineralogist has speculated 
on the forms of silicious minerals and fossils, he generally 
has miYed d priori at the conclusion that they were of aqueous 
origin ; the geologist, on the other hand, has assumed them 
mostly as due to igneous action. M. Brogniart was the first 
to point out the true theory of the silicification in fossil woods, 
in an able paper published in the " Dictionnaire d'Histoire 
Naturelle." In 1828 Von Buch communicated a paper to the 
Academy of Sciences of Berlin, in which he boldly asserts that 
the silicifying process never immediately attacks the calcare- 
ous shell ; that it develops itself only upon the organic sub- 
